ADP-ribosylation factors (Arfs) are a family of GTP-binding proteins that are ubiquitous in eukaryotic cells. Arfs are essential in yeast, signifying these proteins have an important role. Previous attempts to define that role have found Arfs To be involved in membrane transport and in the maintenance of membrane integrity but fail to provide molecular models that adequately describe the function of Arf. To identify elements in the essential Arf signaling pathway, Dr. Chun-jiang Zhang in Dr. Richard Kahn's laboratory conducted a synthetic lethal screen which found interactions between arf1 and two members of the Drs2 family in yeast. By sequencing homology, these proteins are predicted to be ATP-dependent cation transporters. Drs2, one member of the family, has recently been implicated in lipid transport, possibly as a lipid translocase, or flippase. Either function, cation or lipid transport, could fit into a model describing the function of Arf. The goal of this project is to determine if this family of proteins is involved in the Arf signalling pathway. A series of gene knockouts will be constructed to determine which members of the family genetically interact with arf. Using the information and yeast strains from genetic studies, biochemical studies will be conducted to determine if members of this family of proteins function as cation or lipid transporters. These studies will provide valuable genetic and functional interaction with ARF1.